Internal combustion engines are commonly used on mobile platforms (to propel vehicles such as cars, trucks, airplanes, motorcycles, jet skis, snowmobiles), in remote areas (such as for oil well pumps or electric generators) or in lawn and garden tools (such as lawnmowers, weed-eaters, chainsaws, etc.). There are various types of internal combustion engines, furnaces, boilers, kilns and gasifiers.
Spark type engines utilize a volatile fuel, such as gasoline. A spark plug provides the source of ignition. A typical fuel is gasoline, or in high performance engines, methanol. Compression type engines take in air and compress it to generate the heat necessary to ignite the fuel. Typical compression engines also utilize diesel fuel.
When gasoline is burned, it produces pollutants in the form of hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and soot (particulates). In addition, gasoline in warm climates tends to evaporate due to the presence of volatile organic compounds (VOCs).
Internal combustion diesel engines are commonly used in vehicles. Furnaces and boilers are typically used for home or space heating, electrical generation or propulsion of large ships. Kilns are drying devices. Smaller kilns are used in the manufacture of pottery and ceramics. Larger kilns are used to dry lumber or manufacture cement. Gasifiers are devices which convert solid carbonaceous fuels into CO & H2 synthesis gas which is either combusted or further catalyzed into liquid products.
When diesel, lower distillates, petroleum coke or coal is combusted, these fossils produce pollutants in the form of hydrocarbons (HC), nitrogen oxides (NOx), carbon monoxide (CO) and soot (particulates). Nitrogen oxides and volatile organic components react together in sunlight to form ground level ozone, a component of smog. Diesel has less of a tendency to evaporate than does gasoline. Lower distillate heating oils, bunker oils, coke or coal have even less tendency to evaporate VOC's.
In areas of high use, such as heavy automobile traffic, exhaust emissions from internal combustion engines, furnaces, boilers or kilns plus evaporation from the fuel tanks result in significant air pollution. In some urban areas, a brown haze of pollution frequently hugs the first several hundred feet off of the ground.
Alcohol fuel additives have come into use for internal combustion engines as an oxygenate in order to reduce harmful emissions. In the 1970's, gasohol, a blend of mostly gasoline with some ethanol, was introduced during the Arab oil embargo to extend supplies of gasoline. Unfortunately, at that time, many of the elastomeric engine seals, hoses and gasket components were designed only for gasoline or diesel and deteriorated with the use of ethanol. Since then, engines have become equipped with fluorinated elastomers, which are tolerant to alcohol fuel.
Today, the primary alcohol fuel is ethanol, which is typically fermented from grain (corn, wheat, barley, oats, sugar beets, etc.) in a fermentation process. The ethanol is blended into gasoline in various quantities. “Premium” gasoline, with a higher (Research Octane+Motor Octane)/2 (also known as (R+M)/2) octane rating than “regular” gasoline, is primarily gasoline with 10% ethanol (C2 alcohol). Another ethanol fuel is E-85, which is 85% ethanol and 15% gasoline. Still another alcohol fuel is M-85, which is 85% methanol (C1 alcohol) and 15% gasoline.
Grain ethanol is expensive to produce. Furthermore, producing sufficient quantities of grain ethanol to satisfy the needs of the transportation industry is not practical because food crops are diverted into fuel. Traditionally, grain ethanol has been heavily subsidized by governments. Droughts and government policy towards farming in general (less intervention and payments to farmers) make the supply of grain ethanol uncertain and expensive.
In addition, both methanol and ethanol have a relatively lower energy content when compared to gasoline. Methanol contains about 50,000 Btu's/gallon and ethanol contains about 76,000 Btu's/gallon while gasoline contains about 113,000 Btu's/gal. A motorist notices this when a vehicle running on gasoline achieves more miles per gallon than does a similar vehicle running on alcohol fuels.
Some time ago, lead was added to gasoline to boost its octane rating. The octane rating relates to antiknock properties of gasoline. Lead is being eliminated from gasoline for environmental reasons. For the past twenty years or so, gasoline sold in the United States and many other countries has been blended with 5-15% volumes of methyl-tertiary-butyl-ether (MTBE), an oxygenate, in order to raise the octane rating and to reduce environmentally harmful exhaust emissions.
Unfortunately, MTBE is itself a pollutant, having an objectionable odor and taste and having been classified as a potential human carcinogen. To make matters worse, many gasoline storage tanks have developed leaks. MTBE is highly soluble in water and is low in biodegradability. MTBE features a tertiary carbon bond in its molecule which is difficult for natural organisms, such as bacteria or phytoplankton to break down. Consequently, MTBE has polluted the ground water in many communities. Several U.S. states, including Calif., are phasing out the use of MTBE. This phase out will likely result in an eventual ban of MTBE in the USA and in other countries.
The presently planned replacement for MTBE is fermented grain ethanol, but as discussed above, producing the necessary quantities of grain ethanol to replace MTBE will be problematic in specific regions.
Therefore an effective replacement for MTBE in gasoline is needed. In addition, a fuel is needed to reduce harmful combustion emissions from diesel fuel, jet fuel, lower distillate petroleum fuels, coke and coal to reduce particulate soot, hydrocarbons and carbon monoxide. Furthermore, larger quantities of a higher energy content alcohol fuel are needed than can be produced from grain fermentation for the production of ethanol.
MMT, Methylcyclopentadienyl Manganese Tricarbonyl, has been a controversial gasoline additive for many years. MMT was initially used by refiners in the 1970's chiefly to increase octane but studies have shown that while increasing octane, MMT increases emissions, fouls spark plugs and emission control systems. MMT like MTBE usage is declining in North America and in other developed countries. Mixed alcohols can substitute for the octane increase of MMT while additionally working as an oxygenate to improve combustion efficiency which reduces exhaust emissions.